How to combine Views of a Multi-View Camera in Composite
You might have the intention of the node confused. The View Switch node is intended to combine two stereo images in compositing, not to split them. In the current Compositing Pipeline (which isn't suited for 3D Compositing) you have to save the images or use renderlayers to make unique changes for the left and the right side.

However you can easily view images side by side and save them.


in the non stereoscopic view mode, you can view the images individually by selecting their channels in the image editor

this button toggles individual image display and stereo image display mode

to view a stereo image side-by-side directly from Blender, make Blender fullscreen AltF11 then choose window > set stereo 3D and choose your desired viewing mode; Blenders whole interface will be side by side

with the "display the image in stereo 3d" toggle button you can switch to individual image display, while in side by side view

in other modes (e.g. anaglyph, interlaced) we don't have to make Blender fullscreen



All these viewing settings don't affect how the two images are handled internally. Once you want to save your image, you have to enter the method (with which the two images are combined) again.

Press F3 in the image editor to open up the save dialog. Under Views Format choose stereo 3d, then select the stereo mode (e.g. side-by-side).
(If your working in side-by-side you have the additional option to squeeze the images horizontally, so that the original render dimension will be respected.)